I was trying to keep my discussion in the article as "top level" as possible. It's certainly true that violence takes on some unique characteristics when gender, race, ethnicity, sexual preference, and so on are introduced.
I also think it's likely that further thought would produce more categories than the ones I've listed. It was my aim with this article to provoke thought on some of the root causes of violence, and hope that we can learn to treat it as a multifaceted problem.
I'm grateful for your comments, and certainly welcome additional feedback.